Summary The aim of this work is to propose seismic reliability‐based relationships between the strength reduction factors and the displacement ductility demand of nonlinear structural systems equipped with friction pendulum isolators (FPS) depending on the structural properties. The isolated structures are described by employing an equivalent 2dof model characterized by a perfectly elastoplastic rule to account for the inelastic response of the superstructure, whereas, the FPS behavior is described by a velocity‐dependent model. An extensive parametric study is carried out encompassing a wide range of elastic and inelastic building properties, different seismic intensity levels and considering the friction coefficient as a random variable. Defined a set of natural seismic records and scaled to the seismic intensity corresponding to life safety limit state for L'Aquila site (Italy) according to NTC08, the inelastic characteristics of the superstructures are designed as the ratio between the average elastic responses and increasing strength reduction factors. Incremental dynamic analyses (IDAs) are developed to evaluate the seismic fragility curves of both the inelastic superstructure and the isolation level assuming different values of the corresponding limit states. Integrating the fragility curves with the seismic hazard curves related to L'Aquila site (Italy), the reliability curves of the equivalent inelastic base‐isolated structural systems, with a design life of 50 years, are derived proposing seismic reliability‐based regression expressions between the displacement ductility demand and the strength reduction factors for the superstructure as well as seismic reliability‐based design (SRBD) abacuses useful to define the FPS properties. Copyright © 2016 John Wiley & Sons, Ltd.

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Summary The paper deals with the seismic reliability of elastic structural systems equipped with friction pendulum isolators (friction pendulum system). The behavior of these systems is analyzed by employing a two‐degree‐of‐freedom model accounting for the superstructure flexibility, whereas the friction pendulum system device behavior is described by adopting a widespread model that considers the variation of the friction coefficient with the velocity. With reference to medium soil condition, the uncertainty in the seismic inputs is taken into account by considering a set of artificial records, obtained through Monte Carlo simulations within the power spectral density method, with different frequency contents and characteristics depending on the soil dynamic parameters and scaled to increasing intensity levels. The sliding friction coefficient at large velocity is also considered as random variable modeled through a uniform probability density function. Incremental dynamic analyses are developed in order to evaluate the probabilities exceeding different limit states related to both r.c. superstructure and isolation level defining the seismic fragility curves through an extensive parametric study carried out for different structural system properties. Finally, considering the seismic hazard curves related to a site near L'Aquila (Italy), the seismic reliability of the r.c. superstructure systems is evaluated, and seismic reliability‐based design abacuses are derived with the aim to define the radius in plan of the friction pendulum devices in function of the structural properties and reliability level expected. Copyright © 2016 John Wiley & Sons, Ltd.

Summary This study aims at proposing seismic reliability‐based relationships between the behavior factors and the displacement demand for nonlinear hardening and softening structures isolated by friction pendulum system devices considering several structural properties. An equivalent 2dof model having both a hardening and softening postyield slope is used to describe the superstructure behavior, whereas a velocity‐dependent model is adopted for the friction pendulum system response. The yielding characteristics of the superstructures, related to life safety limit state, are designed according to the seismic hazard of L'Aquila site (Italy) for increasing behavior factors, as provided from NTC08. Considering natural seismic records and several elastic and inelastic building properties, different postyield hardening and softening stiffness values, different seismic intensity levels, and modeling the friction coefficient as a random variable, incremental dynamic analyses are performed to evaluate the seismic fragility of these structural systems. By means of the convolution integral between the fragility curves and the seismic hazard curves corresponding to L'Aquila site (Italy), the reliability curves of the equivalent hardening and softening base‐isolated structural systems, with a lifetime of 50 years, are defined. Specifically, seismic reliability‐based linear and multilinear regression expressions between the displacement ductility demand and the behavior factors for the superstructure as well as seismic reliability‐based design abacuses for the friction pendulum devices are proposed.

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This paper presents the most significant results obtained within a broad range of experimental tests aimed at evaluating both the effectiveness and robustness of the Base Isolation (BIS) and Tuned Mass Damper (TMD) combined control strategy (BIS&TMD). After a brief description of the experimental model set-up, the paper describes the identification procedures for the fixed base structure, the base isolated structure and the base isolated structure equipped with a mass damper system. The main experimental results, representing the dynamic response of a small-scale model to scaled recorded earthquake excitations, are later presented and discussed. Finally, the effectiveness and robustness of the combined control strategy is investigated by comparing the model's dynamic response, in particular the reduction in relative displacements and absolute accelerations due to the application of different mass damping systems are evaluated.

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